March 28, 2024, 03:34:50 PM
Forum Rules: Read This Before Posting


Topic: Problem of the week - 09/07/2012  (Read 31073 times)

0 Members and 1 Guest are viewing this topic.

Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27634
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Problem of the week - 09/07/2012
« on: July 09, 2012, 07:44:27 AM »
When 1.000 g of a strong oxidizer A was dissolved in water, solution initially became wine red, but soon the substance decomposed, producing 85 mL (STP) of a dry gas B and 0.4032 g of a red-brown solid C. Drop of a concentrated, oxidizing acid, added to the alkaline filtrate, produced white precipitate D. Red-brown solid C was dissolved in a hydrochloric acid, and 1 g copper wire was put into the solution. After reaction ended, mass of the wire left was 0.8396 g.

Name all substances, write all reaction equations.


This one is not very difficult, call it a side product of my current work on the stoichiometry calculator  :P
« Last Edit: July 12, 2012, 04:33:44 PM by Borek »
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Rutherford

  • Sr. Member
  • *****
  • Posts: 1868
  • Mole Snacks: +60/-29
  • Gender: Male
Re: Problem of the week - 09/07/2012
« Reply #1 on: July 12, 2012, 11:47:06 AM »
If I could think of a gass that has the molar mass 157.27g/mol.

Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27634
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Problem of the week - 09/07/2012
« Reply #2 on: July 12, 2012, 12:09:11 PM »
No idea where did you get 157 g/mol from?
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Rutherford

  • Sr. Member
  • *****
  • Posts: 1868
  • Mole Snacks: +60/-29
  • Gender: Male
Re: Problem of the week - 09/07/2012
« Reply #3 on: July 12, 2012, 12:44:46 PM »
The number of moles of the gass B is 0.085/22.4=0.003795, and its mass is 1-0.4032=0.5968g. M=0.5968/0.003795=157g/mol.

Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27634
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Problem of the week - 09/07/2012
« Reply #4 on: July 12, 2012, 12:53:06 PM »
No, mass is off.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Rutherford

  • Sr. Member
  • *****
  • Posts: 1868
  • Mole Snacks: +60/-29
  • Gender: Male
Re: Problem of the week - 09/07/2012
« Reply #5 on: July 12, 2012, 12:57:16 PM »
I guess you mean that not the whole amount decomposed.

Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27634
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Problem of the week - 09/07/2012
« Reply #6 on: July 12, 2012, 01:30:00 PM »
Decomposition was stoichiometric and went to completion.
« Last Edit: July 12, 2012, 02:55:38 PM by Borek »
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Rutherford

  • Sr. Member
  • *****
  • Posts: 1868
  • Mole Snacks: +60/-29
  • Gender: Male
Re: Problem of the week - 09/07/2012
« Reply #7 on: July 12, 2012, 04:09:23 PM »
Then why is the mass off?

Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27634
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Problem of the week - 09/07/2012
« Reply #8 on: July 12, 2012, 04:25:06 PM »
I see now that the wording is not perfect, but you ignored information about the filtrate.
« Last Edit: July 12, 2012, 04:35:50 PM by Borek »
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Rutherford

  • Sr. Member
  • *****
  • Posts: 1868
  • Mole Snacks: +60/-29
  • Gender: Male
Re: Problem of the week - 09/07/2012
« Reply #9 on: July 12, 2012, 05:00:44 PM »
Oh yes, my mistake, sorry.

Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27634
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Problem of the week - 09/07/2012
« Reply #10 on: July 16, 2012, 05:20:06 AM »
Looks like week was not enough... Which most likely means nobody but Raderford even tried  :-\

Deadline extended, I am going to wait for another week.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Ann1234

  • Regular Member
  • ***
  • Posts: 63
  • Mole Snacks: +4/-0
  • Gender: Female
Re: Problem of the week - 09/07/2012
« Reply #11 on: July 23, 2012, 10:10:22 AM »
Looks like week was not enough... Which most likely means nobody but Raderford even tried  :-\

Deadline extended, I am going to wait for another week.

Borek, is not that we are not trying...I actually tried 2 times (last was yesterday) but I got stuck finding the strong oxidizer.... :(

Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27634
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Problem of the week - 09/07/2012
« Reply #12 on: July 23, 2012, 01:17:32 PM »
Borek, is not that we are not trying...I actually tried 2 times (last was yesterday) but I got stuck finding the strong oxidizer.... :(

Unfortunately I am away, so I can't answer immediately - but perhaps if you will post what you tried and what you found, it will either wait for a day or two till I will be able to comment, or it will trigger comments from others. I think there are things that should be obvious, like the identity of the red-brown solid.

OK, if someone is trying, I am extending it for another week.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Ann1234

  • Regular Member
  • ***
  • Posts: 63
  • Mole Snacks: +4/-0
  • Gender: Female
Re: Problem of the week - 09/07/2012
« Reply #13 on: July 23, 2012, 06:41:40 PM »
okay....I think the red brown solid may be Iron (III) Oxide, and I found that solutions of Fe(OH)3 are wine red...but this hydroxide in water seems to be stable...so I got stuck again  :(

Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27634
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Problem of the week - 09/07/2012
« Reply #14 on: July 25, 2012, 01:47:50 PM »
Good idea about iron(III) - but it is not the original compound. Its a product of the original compound decomposition.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Sponsored Links